Sandblasting is known as one of the techniques for patterning the surface of a substrate such as glass, stone, plastics, ceramics, leather, and wood. Sandblasting is carried out by a process using a stencil in which a rubber sheet, paper, etc. is stuck to the substrate and cut with a cutter, etc. to form a stencil pattern, and an abrasive is made to strike against the substrate to selectively abrade the substrate or a process using a photomask in which a photosensitive layer of a photosensitive composition is provided on the substrate, a mask pattern is formed by photolithography, and an abrasive is made to strike against the substrate to selectively abrade the substrate. The former process involves troublesome operations with low working efficiency. On the other hand, the latter photolithographic process achieves high working efficiency, enables fine processing, and is effective for producing circuit boards composed of a metallic pattern and an insulating pattern, particularly for the formation of a metallic wiring pattern and an insulating pattern made of ceramics, fluorescence substances, etc. of a plasma display panel.
Photosensitive compositions which have been proposed to date for use in the lithographic sandblasting include a composition comprising a urethane prepolymer having an ethylenically unsaturated group at the terminal, a monofunctional ethylenically unsaturated compound, and a polymerization initiator (see JP-A-60-10242), a composition comprising an unsaturated polyester, an unsaturated monomer, and a photopolymerization initiator (see JP-A-55-103554), and a composition comprising polyvinyl alcohol and a diazo resin (see JP-A-2-69754). The term "JP-A" as used herein means an unexamined published Japanese patent application. However, these photosensitive resin compositions are disadvantageous in that film thickness control is difficult, sensitivity, adhesion to a substrate and resistance to sandblasting are insufficient, and fine processing is difficult. In order to overcome these disadvantages, JP-A-6-161098 proposed a photosensitive composition for sandblasting which comprises a urethane prepolymer terminated with an ethylenically unsaturated group as a main component, a cellulose derivative, and a polymerization initiator. Although this composition is excellent in not only alkali developability but sensitivity, adhesion to a substrate, and elasticity and softness after patterning and is superior in sandblasting resistance to conventional photosensitive compositions, it is still unsatisfactory in performance in fine pattern formation for practical use. It has therefore been keenly demanded to develop a photosensitive composition having improved properties.